Reverse a string using stack

LIST OF PROGRAMS

#include<stdio.h>
#include<conio.h>
#include<process.h>
void push();
void display();
int top=-1,ch=1,lim,tmp=-1;
char stack[100],item;
void push()
{
if(top<lim-1)
{
printf("ENTER CHARACTER TO BE STORED");
fflush(stdin);
scanf("%c",&item);
top=top+1;
stack[top]=item;
}
else
printf("STACK OVERFLOW");
}
void display()
{
tmp=top;
tmp=0;
printf("\nORIGINAL STRING ");
while(tmp<=top)
printf("%c",stack[tmp++]);
printf("\nREVERSED STRING ");
while(tmp>=0)
{
printf("%c",stack[tmp--]);
}
}
void main()
{
clrscr();
printf("ENTER MAXIMUM LIMIT ");
scanf("%d",&lim);
do
{
printf("\n ENTER 1 FOR PUSH\nENTER 2 FOR DISPLAY \n ENTER ANY OTHER NUMBER FOR EXIT ");
fflush(stdin);
scanf("%d",&ch);
switch(ch)
{
case 1 : push();
break;
case 2: display();
break;
default:exit(0);
}
}while(ch==1||ch==2);
getch();
}//click on the pic to enlarge it 

]

LIST OF PROGRAMS